The Dirichlet Problem for the Perturbed Elliptic Equation

In this paper, the authors consider the construction of one class of perturbed problems to the Dirichlet problem for the elliptic equation. The operators of both problems are isospectral, which makes it possible to construct solutions to the perturbed problem using the Fourier method. This article focuses on the Dirichlet problem for the elliptic equation perturbed by the selected variable. We established the spectral properties of the perturbed operator. In this work, we found the eigenvalues and eigenfunctions of the perturbed task operator. Further, we proved the completeness, minimal spanning system, and Riesz basis system of eigenfunctions of the perturbed operator. Finally, we proved the theorem on the existence and uniqueness of the solution to the boundary value problem for a perturbed elliptic equation

Biomechanické studie vnitřního páteřního hrudního fixátoru MACSTL

Unstable fractures of the thoracic spine in humans represent a serious social and economic issue. They may lead to persistent consequences and chronic disease. The anatomical and biomechanical characteristics of the thoracic spine are different from all the other spinal parts due to its higher mobility. The vertebrae of the chest area are less mobile, conferring a higher degree of rigidity to the spine. To destabilize this relatively rigid system, a considerable force is necessary. The treatment of unstable spinal fractures is solely surgical. The decompression of the spinal canal with reposition and stabilisation of the fracture is indicated urgently. This intervention is performed mostly from the posterior approach in the first phase. However, the anterior spinal column is the structure responsible for the stability of the spine. Therefore, the recent advances in spine surgery focus on this area of expertise. For this reason, we carried out a bio-mechanical study aimed at assessing the effectiveness of two surgical tactics used. The study consisted of comparative experiments performed by computer-aided device on segments of pig cadavers (n = 5). The experiment involved a comparison of segments of the thoracic spine under the following conditions: an anatomically intact segment, a spine segment with an artificially created anterior instability, and a segment with an applied internal fixator. The experiment compared the mechanical characteristics of these segments. The experiment has demonstrated that after application of the internal fixator used for stabilisation of the injured anterior spinal column at defined pre-loading of 200 N, the stability of damaged spinal segment in torsion increased twofold. It was also verified that sufficient stability can be ensured using the Modular Anterior Construct System (MACSTL) implant for ventral stabilisation of thoracic spine unstable injuries. Endoscopic application of this implant represents an additional advantage of this surgical procedure.Nestabilní zlomeniny hrudní páteře lidí, představují vážný sociální a ekonomický problém. Mohou vést k trvalým následkům a chronickému onemocnění. Anatomické a biomechanické charakteristicky hrudní páteře jsou odlišné od všech dalších její částí, díky jejích vyšší pohyblivosti. Obratle z oblasti hrudního koše jsou méně pohyblivé v důsledku vyšší tuhosti této soustavy. K destabilizaci relativně tuhé soustavy, je nezbytné značné síly. Léčba nestabilních páteřních zlomenin je možná výhradně chirurgicky. Je nutné provést dekompresi kanálu, repozici a stabilizaci zlomeniny. Toto je většinou provedeno v první fázi ze zadního přístupu. Nicméně, struktura přední části páteře je odpovědná za její stabilitu. Zaměření na tuto oblast přináší pokroky v současné páteřní chirurgii. Z tohoto důvodu, jsme uskutečnili biomechanickou studii zaměřenou na hodnocení efektivity dvou chirurgických postupů. Práce je založena na experimentální srovnávací studii na prasečích páteřních segmentech (n = 5). Experiment zahrnuje biomechanické srovnání páteřního segmentu v těchto stavech: anatomicky nedotčený, páteřní segment s uměle vytvořenou přední nestabilitou, a segment s aplikovaným vnitřním fixátorem. Páteřní segment byl zatěžován kombinací tahového předpětí o velikosti 200 N a zkroucení segmentu o požadovaný úhel. Uvedeným způsobem byly zatěžovány vzorky v dříve uvedených stavech. Experiment prokázal, že přední modulární systém (MACSTL) dostatečná stabilizuje hrudní páteřní nestability v trumatologii. Další výhoda tohoto chirurgického postupu spočívá v endoscopické aplikaci

Print Management System Model in a Large Organization

This article is focused on the analysis and solution of the issue of a printing system model in a large organization. It provides an overview of the current stat29e of the organization and its current printing system. Based on the information about strengths and weaknesses, the most suitable solution for the given organization was designed and subsequently implemented. The created design meets all the requirements required by the company, while minimizing the threats that the deployment of the new system and the resulting changes may have. The work also describes various ways of dealing directly with change, whether when dealing with the old printing system or preparing employees for its change. The new system brings clear unification of the press, its monitoring and administration under the supervision of its own employees without the need for external companies or support

Properties of Broezel static probe

The properties of flat static probe designed by Broezel and used in sailplanes are investigated for its planned use in low speed tunnel. Both the numerical CFD model and experiment in low speed wind tunnel confirm yaw insensitivity of the static pressure measured by the probe. The results indicate that the probe is sufficiently accurate for its planned use in wind tunnel measurements

Customer-Oriented Quality of Service Management Method for the Future Intent-Based Networking

The rapid development and spread of communication technologies is now becoming a global information revolution. Customers have a need for communication services, which could be flexibly configured in accordance with their Quality of Experience (QoE) requirements. Realizing the close connection between customer experience and profitability, the service provider has been placing more and more attention on customer experience and QoE. The traditional quality of service management method based on SLA (Service Level Agreement) is not sufficient as a means to provide QoE-related contracts between service providers and customers. The current SLA method is mostly limited and focused on technical aspects of QoS (Quality of Service). Furthermore, they do not follow on the network the principles and semantic approach to the QoS specification for a communication service using QoE parameters. In this paper, we propose a customer-oriented quality of service management method for future IBN (Intent-Based Networking). It is based on a new QoE metric on a scale from 1 to 5, which allows one to take into account the commercial value of e-services for customers. Based on this approach, the network configuration and functionality of network equipment automatically changes depending on customer requirements. To implement the new method of service quality management, an algorithm for routing data packets in the network was developed, taking into account the current load of the forecast path. The algorithm of billing system functioning in conditions of customer-oriented quality management in telecommunication networks has been created. To investigate the effectiveness of the proposed method of service quality management with the traditional SLA method, we developed a simulation network model with the implementation of two approaches. By conducting a simulation, it was determined that the proposed method gives an average gain of 2–5 times for the criterion of the number of customers who require high quality of experience of the service

Factors Affecting Measurements of IOP Using Non-Contact Eye Tonometer

The objective measurement of intraocular pressure (IOP) represents the identification of the symptoms of some diseases, e.g. glaucoma. This objective measurement can only be achieved by correct calibration of tonometers. Today, there is no uniform methodology for this calibration. Therefore, we introduce potential sources of error and try to quantify their contributions in this paper. Subsequently, a calibration standard containing an artificial cornea with similar properties to the human one should be designed

Texture Hardening Observed in Mg–Zn–Nd Alloy Processed by Equal-Channel Angular Pressing (ECAP)

The addition of Nd significantly improves the mechanical properties of magnesium alloys. However, only limited amounts of Nd or other rare earth (RE) elements should be used due to their high price. In this study, a low-alloyed Mg–1% Zn–1% Nd (ZN11) alloy was designed and processed by hot extrusion and subsequent equal-channel angular pressing (ECAP) in order to achieve a very fine-grained condition with enhanced strength. The microstructure, texture, and mechanical properties were thoroughly studied. The microstructure after 8 passes through ECAP was homogeneous and characterized by an average grain size of 1.5 µm. A large number of tiny secondary phase precipitates were identified as ordered Guinier–Preston (GP) zones. Detailed analysis of the Schmid factors revealed the effect of the texture on deformation mechanisms. ECAP processing more than doubled the achieved yield compression strength (YCS) of the ZN11 alloy. Significant strengthening by ECAP is caused by grain refinement and the formation of ordered Guinier–Preston zones and particles of a secondary γ-phase

Social networking security during COVID-19 : a systematic literature review

During the Covid-19 Pandemic, the usage of social media networks increased exponentially. People engage in education, business, shopping, and other social activities (i.e., Twitter, Facebook, WhatsApp, Instagram, YouTube). As social networking expands rapidly, its positive and negative impacts affect human health. All this leads to social crimes and illegal activities like phishing, hacking, ransomware, password attacks, spyware, blackmailing, Middle-man-attack. This research extensively discusses the social networking threats, challenges, online surveys, and future effects. We conduct an online survey using the google forms platform to collect the responses of social networking sites (SNS) users within Pakistan to show how SNS affects health positively and negatively. According to the collected response, we analyzed that 50% of the users use SNS for education purposes, 17.5% use it for shopping purposes, 58.2% use it for entertainment, 37.1% use it for communication, and 9.8% use it for other purposes. According to the response, the excessive use of SNS affects the health that 9.8% users face the physical threat, 42.8% user faces mental health issues due to excessive or inappropriate use of SN, and 50.5% users feel moral threat using Social sites. Finally, we conclude our paper by discussing the open challenges, conclusions, and future directions

The Influence of Milling and Spark Plasma Sintering on the Microstructure and Properties of the Al7075 Alloy

The compact samples of an Al7075 alloy were prepared by a combination of gas atomization, high energy milling, and spark plasma sintering. The predominantly cellular morphology observed in gas atomized powder particles was completely changed by mechanical milling. The continuous-like intermetallic phases present along intercellular boundaries were destroyed; nevertheless, a small amount of Mg(Zn,Cu,Al)2 phase was observed also in the milled powder. Milling resulted in a severe plastic deformation of the material and led to a reduction of grain size from several µm into the nanocrystalline region. The combination of these microstructural characteristics resulted in abnormally high microhardness values exceeding 300 HV. Consolidation through spark plasma sintering (SPS) resulted in bulk samples with negligible porosity. The heat exposition during SPS led to precipitation of intermetallic phases from the non-equilibrium microstructure of both gas atomized and milled powders. SPS of the milled powder resulted in a recrystallization of the severely deformed structure. An ultra-fine grained structure (grain size close to 500 nm) with grains divided primarily by high-angle boundaries was formed. A simultaneous release of stored deformation energy and an increase in the grain size caused a drop of microhardness to values close to 150 HV. This value was retained even after annealing at 425 °C

Nanocrystalline Al7075 + 1 wt % Zr Alloy Prepared Using Mechanical Milling and Spark Plasma Sintering

The microstructure, phase composition, and microhardness of both gas-atomized and mechanically milled powders of the Al7075 + 1 wt % Zr alloy were investigated. The gas-atomized powder exhibited a cellular microstructure (grain size of a few µm) with layers of intermetallic phases along the cell boundaries. Mechanical milling (400 revolutions per minute (RPM)/8 h) resulted in a grain size reduction to the nanocrystalline range (20 to 100 nm) along with the dissolution of the intermetallic phases. Milling led to an increase in the powder’s microhardness from 97 to 343 HV. Compacts prepared by spark plasma sintering (SPS) exhibited negligible porosity. The grain size of the originally gas-atomized material was retained, but the continuous layers of intermetallic phases were replaced by individual particles. Recrystallization led to a grain size increase to 365 nm in the SPS compact prepared from the originally milled powder. Small precipitates of the Al3Zr phase were observed in the SPS compacts, and they are believed to be responsible for the retainment of the sub-microcrystalline microstructure during SPS. A more intensive precipitation in this SPS compact can be attributed to a faster diffusion due to a high density of dislocations and grain boundaries in the milled powder